Facsimile devices are subject to various device noises that are produced by internal mechanisms during operation thereof. For example, actuators such as motors for feeding documents and recording sheets tend to generate electrical noise during the transmission and reception of image data.
At the start of a data communication process, a protocol handshake signal known as a TCF (training check) signal for checking the status of the transmission line is transmitted from a calling facsimile device to a called facsimile device. Usually, the actuators are not energized during transmission and reception of the TCF signal since no image data is being sent.
Conventional facsimile devices have certain problems because device noise produced while the protocol TCF signal is being transmitted and received, and device noise produced while image data is being transmitted and received have different levels. More specifically, while the TCF signal Is being transmitted and received, the protocol training check carried out by the TCF signal may be successful since the actuators are not energized and little device noise is generated. However, while image data is being transmitted and received, a relatively high level of device noise is produced since the actuators are energized. If the produced device noise is greater than a predetermined level, then decoding errors or communication errors will occur.
It is difficult or almost impossible to completely remove device noise through hardware design approaches.